Dropout compensation in magnetic tape channels by adaptive equalization and coding

Abstract

A simple adaptive extended partial response IV (EPR4) equalizer with an adaptive gain controller driven by a threshold detector with relaxed thresholds can be applied effectively on fading tape channels. The equalizer closely approximates the performance of the optimal EPR4 equalizer. Other EPR4 equalizers with certain advantageous features (the EPR4. equalizer with decision feedback and the PW50-based EPR4 equalizer) are also studied. The parallel concatenated parity check (PCPC) code with iterative decoding is quite effective in mitigating the dropout effect. The complexity/performance tradeoffs of the PCPC code seem favorable compared to the low-density parity check code or to the turbo code.